Effect Of Base Current Research Articles

A 3.0-V 4.2-μA 2.23-ppm/°C BGR with cross-connected NPNs and base-current compensation

This paper presents a high-precision, low-power bandgap voltage reference with a 3.0 V output voltage suitable for battery-management systems. Compared to Brokaw's type bandgap references (BGRs), Cross-connected NPN transistors facilitate higher output voltages without the necessity of operational amplifiers and are unaffected by the current-mirror mismatch. Base-current compensation is proposed to address the effect of base current on voltage output temperature characteristics at low power consumption. A piecewise exponential curvature correction stains high-order compensation for the nonlinear characteristic of base-emitter voltage. Experimental results of the proposed BGR implemented in a 0.18-μm Bipolar-CMOS-DMOS (BCD) process demonstrate that the temperature coefficient is 2.23 ppm/°C over the range of −40 °C–120 °C. The line regulation is 0.2 mV/V at a 5–6 V supply voltage with a supply current of only 4.2 μA. The die area of the fabricated BGR is 0.105 mm2.

Performance of piezoelectric semiconductor bipolar junction transistors and the tuning mechanism by mechanical loadings

A coupling model is established on piezoelectric semiconductor bipolar junction transistors (PS-BJT) subjected to mechanical loadings by abandoning depletion layer approximation and low injection assumption. Effect of base region on device performance and interaction between emitter/base junction (E/B) and base/collector junction (B/C) are investigated. It is found that too small a base width will cause B/C to extract electrons directly from emitter region, implying that an electron passageway will be excited to link from collector- to emitter-region by striding over base-region (abbreviated as “EP-CE” hereafter). We particularly clarify that the current produced by electrons flowing across EP-CE is independent of electron-hole recombination in E/B, which means that this current has not yet been bestowed on the information of base current. “Information of base current” refers to dispatching information of base current on the electrons in emitter region. Thus, a current from EP-EC cannot be reckoned in the amplification effect of base current. Our investigations show that base width should not be designed too small to avoid EP-CE, which has not been revealed before. As regards to tuning PS-BJT performance by mechanical loadings, we revealed the mechanism as follows: 1) raising electron-hole recombination rate inside E/B to reduce resistivity such that more electrons can be driven from emitter- to base-region; 2) elevating electron conductivity in base-region for easier pass of electrons; 3) promoting attractive ability of B/C on electrons such that more electrons cross the interface. Numerical results show that transmission characteristics can be greatly increased as expected by mechanical tuning.

Temperature Dependence of Current Gain, Ideality Factor, and Offset Voltage of AlGaAs/GaAs and InGaP/GaAs HBTs

This paper elucidates the stabilities of the dc current gain, ideality factor, and offset voltage against variations in temperature and currents for GaAs-based heterojunction bipolar transistors (HBTs). The InGaP/GaAs HBT markedly reduces the offset voltage and improves the temperature stability of the dc current gain relative to those of AlGaAs/GaAs benchmark devices. The relative insensitivity of the offset voltage in the InGaP/GaAs HBT to the temperature is established by comparison with AlGaAs/GaAs counterparts. One of the more intriguing aspects of these two HBTs is the replacement of the AlGaAs emitter with the InGaP emitter to improve the temperature stability of the offset voltage. Specifically, the effect of the base current on the offset voltage is abnormal in these devices. In this paper, the conventional Ebers-Moll model cannot account completely for our observed phenomena. Accordingly, the results herein (improved temperature stability of the offset voltage in the InGaP emitter HBT and the uncommon base current effect in these two devices) are interpreted in terms of a physics-based analytical model. A strong consistency existed between the experimental data and the theory. Additionally, some reasonable predictions (not obtained from the measured data) of the specific physically based model are presented. The large-signal model provides a description of device performance that will be of use to device engineers and designers.

Investigations of impact ionization phenomena in advanced transistors and speed-power improvement of BiMOS SRAM cells based on reverse base current effect

The experimental investigations of base reverse current of integrated Si polysilicon emitter bipolar transistor and its multiplication coefficients ( M−1) vs. U cb at different I E when the device is driven at constant emitter currents are represented. Current crowding effect induced by impact ionization in advanced Si transistors and intrinsic complex instabilities and limitations affecting multiplication coefficients under variable high electric fields at low and high emitter current densities are analysed. The speed-power potential and limitations of high-density memory cells based on reverse base current effect are discussed. Speed-power possibilities and limitations of scaled down BiMOS SRAM cells are examined using numerical simulation of their capabilities to work in a memory system at different conditions.

BiCMOS bandgap voltage reference with base current compensation

The effect of base current on the relationship between reference and output voltages in a bandgap voltage reference circuit is considered. The modifications developed to compensate for this influence in a standard reference circuit are described. The compensation is achieved by measuring the collector current of one of the transistors, creating a positive temperature coefficient current and introducing a p-channel current doubler in the base circuit of the measuring transistor. The simulation results demonstrate the efficiency of the proposed improvement.

A new static memory cell based on the reverse base current effect of bipolar transistors

A SRAM cell that consists of a bipolar transistor and an MOS transistor is proposed. The cell's principle of operation is based on the reverse base current (RBC) of a bipolar transistor. It has been fabricated by conventional BiCMOS technology, using double-poly Si. A cell size of 8.58 mu m/sup 2/ is realized in a 1.0- mu m ground rule. The mechanism and characteristics of this cell are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A phenomenological model of switching in metal-thin insulator-semiconductor-semiconductor devices: A development of the analogy with the thyristor

The present understanding of the basic operational parameters of two- and three-terminal metal-thin insulator-semiconductor-semiconductor (MISS) switches is reviewed briefly. Although several different approaches have been tried, since the first descriptions of MISS devices in 1972, agreement between theory and experiment is at best semiquantitative. Even a parameter as basic as the (dc) static threshold voltage is not accurately predicted by current models. In the present paper a thyristor analogy is developed more fully and quantitatively, drawing upon well-established theories of instabilities in p-n-p-n structures. By making the justified assumption that in MISS devices inversion at the semiconductor-insulator interface forms only when the switching voltage is attained, it is possible to predict the threshold voltage and its temperature dependence in two-terminal structures. The effect of base current on the switching voltage of three-terminal devices can similarly be accounted for in a phenomenological way. Comparisons are made with published data from several sources and the thyristor model is shown to provide good agreement between experimental data and calculated parameters (values of the threshold voltage) for MISS devices with silicon oxide insulating layers.

A new type transistor tetrode

The density of injected current from the emitter of a junction transistor is never uniform over the emitter area because of the biasing effect of base current. In a normal three-terminal transistor, the result is to decrease the effective emitter voltage at distances far away from the base contact. In a normal tetrode, the emission is squeezed towards one of the base contacts with a net decrease in the base resistance.